report shorter - Antarctic Science Bursary

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Giulia Airoldi (University of Otago, New Zealand)
Project: Clues from the Ferrar Province: dikes and sills in the Transantarctic Mountains record
interaction of flood-basalt magmas with tectonics at the time of Gondwana break-up.
Contribution: to consult on dyke emplacement in Large Igneous Provinces, and present early results at
IAVCEI in Iceland
The Jurassic Ferrar Large Igneous Province (FLIP) of Antarctica represents massive amounts of
magma, emplaced both beneath the Transantarctic Mountains (TAM) and at the surface, related to early
break-up of Gondwanaland. Remnants of magmatic systems now exist as volcaniclastic deposits, lava
flows and intrusive complexes. Ferrar Dolerite intrusions, exposed over ~3500 km2 from the TAM up
to southern Australasia, represent most of the FLIP rocks. Previous studies show that large sills prevail
over dikes and that the latter do not form the regional swarms normally encountered along extensional
boundaries. The existence of vertical feeders or magma chambers is debated.
My project models a representative part of the FLIP plumbing system, by describing overall
geological features and characteristics of the rocks from selected intrusive complexes along the TAM.
Photogeology and structural field observations for three localities between South Victoria Land (SVL)
and the Dry Valleys are being combined with study of dolerite petro-fabrics, investigated using
petrography and rock-magnetism (anisotropy of magnetic susceptibility, AMS). My results show that
localized arrays of Ferrar dikes either interconnect sill-fronts at distinct stratigraphic levels, or were fed
into and away from ancient volcanic edifices. Intrusion geometry and AMS directions obtained for
most dikes so far record: i) variations in magma-flow in distinct generations of cracks and ii) major
control by the magmatic stress-field over the tectonic conditions on both the magma-flow within the
dikes and the propagation of individual cracks and dike sets.
The Antarctic Science Bursary supported presentation of field and initial laboratory results at
the XXVIII IAVCEI Assembly (Iceland, August 2008). Discussions with other scientists attending the
conference provided a unique opportunity to place my Antarctic work on LIP magmatic systems in the
context of a great range of work on Icelandic magmatism, as well as work globally on analogous
magmatic processes. The setting of the meeting in Iceland is sparsely settled, but highly modified highlatitude landscape increased my appreciation of the importance for Antarctica of continued strong
environmental protection.
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